Is fracking behind Oklahoma’s earthquakes?

One of the strongest earthquakes in the history of Oklahoma hit near the town of Sparks on Saturday night. At 5.6 in magnitude, it was the bell-ringer of a series of shakes. What is not clear is where this unusual seismic activity is coming from. The Oklahoman reported:

After the main shock, there were 12 temblors registering at magnitudes of 3.0 or higher and more than 70 quakes with magnitudes of 1.0 to 2.5, Oklahoma Geological Survey research scientist Amie Gibson said Sunday.

“We really hope that the 5.6 was the main shock because I don’t want to see anything like that again, personally. It would be ignorant to assume anything right now, because who would assume that we’d have the two biggest ones in one day?” Gibson said.

Before Saturday night, the strongest earthquake recorded was April 9, 1952, in El Reno, according to the geological survey. Its magnitude was 5.5.

“We have not a clue,” Mr. Holland said of the increase. “It could be a natural cycle; we just don’t know.”

Unfortunately the New York Times reporter either didn’t ask or didn’t know about a study that Mr. Holland published in August 2011 that explored the possible connection between hydraulic fracturing and increased seismic activity in a similar series of quakes that occurred south of Sparks. The report — “Examination of Possibly Induced Seismicity from Hydraulic Fracturing in the Eola Field, Garvin County, Oklahoma” — goes through the existing evidence linking fracking and earthquakes step-by-step. Holland says there is a possibility that the two are linked but that data uncertainties keep him from saying so with absolute conviction. From the summary of the report (emphasis mine):

On January 18, 2011, The Oklahoma Geological Survey (OGS) received a phone call from a resident living south of Elmore City, in Garvin County, Oklahoma, that reported feeling several earthquakes throughout the night. The reporting local resident had also offered that there was an active hydraulic fracturing project occurring nearby.

Upon examination there were nearly 50 earthquakes, which occurred during that time. After analyzing the data there were 43 earthquakes large enough to be located, which from the character of the seismic recordings indicate that they are both shallow and unique.

[..]

The strong correlation in time and space as well as a reasonable fit to a physical model suggest that there is a possibility these earthquakes were induced by hydraulic fracturing. However, the uncertainties in the data make it impossible to say with a high degree of certainty whether or not these earthquakes were triggered by natural means or by the nearby hydraulic fracturing operation.

Mr. Holland is skating into dangerous territory with this research. Oklahoma is a national leader in natural gas production, and taxes on it are a big source of revenue. From OK Policy Institute:

Oklahoma is among the nation’s largest producers of both natural gas and oil: In 2009, almost 1.9 trillion cubic feet of natural gas were produced in Oklahoma. Oklahoma’s natural gas output represented 8.5 percent of total U.S. production, trailing only Texas (7.7 trillion cubic feet) and Wyoming (2.5 trillion).

So it’s all eyes on the Okie shakes. This may be just an odd series of seismic events. Or it maybe the canary in the coal mine for hydraulic fracturing.

BTW: The largest gas producers in Oklahoma are not local boys but some pretty heavy hitters.

Source: Oklahoma Corporation Commission: 2009 Report on Oil and Natural Gas Activity Within the State of Oklahoma (page 124)

A study by a group of geologists, commissioned by the company-under-scrutiny Cuadrilla and based on technical reports from a variety of survey companies , found that the fluids likely caused the pre-existing division between the rocks to lubricate. This allowed the rock formations to slide against each other more easily, causing the 2.3 and 1.5 magnitude quakes.

According to the report, “Most likely, the repeated seismicity was induced by direct injection of fluid into the fault zone. since the pressure spread out over a larger area causing the largest event 10 hours after the injection.”

Keller said the chance is remote that oil and gas drilling activities in the area had anything to do with the earthquakes Saturday. The quakes were centered more than two miles below the ground, far below drilling in the area.
“It’s way below any depth anybody is pumping or injecting or anything else, and it isn’t a particularly active area, oil and gas-wise,” Keller said.
Residents in nearby states have blamed hydraulic fracturing and gas injection wells for small earthquakes, and the Arkansas Oil and Gas Commission shut down some injection wells in an area where there were concerns that earthquakes were linked to oil and gas activity.
Holland has studied the swarm of smaller quakes in Oklahoma for links to the oil and gas industry, but has said he found little evidence they’re related.

You’re barking up the wrong tree. Fracture stimulations are not of a magnitude or at a depth to cause the large earthquakes experienced in central Oklahoma.
These are almost certainly being caused by the tremendous volumes of water being disposed into the Arbuckle Formation in this area. Most of this water is produced as a result of the exploitation of what is locally called the Hunton de-watering play.
The water injected into the Arbuckle is winding up in the pre-Cambrian basement through movement along an extensive vertical fracture system.